Cylinder head cover for a cylinder head of an internal combustion engine

ABSTRACT

A cylinder head cover for a cylinder head of an internal combustion engine having a gasket element between the cylinder head and the cylinder head cover in which the gasket element includes a vacuum chamber which is open on at least one side and produces a seal between the cylinder head cover and the cylinder head when a vacuum is applied.

BACKGROUND OF THE INVENTION

The invention relates to a cylinder head cover for a cylinder head of an internal combustion engine with a gasket element between the cylinder head cover and cylinder head.

Known cylinder head covers are placed on the cylinder head of an internal combustion engine and affixed to the cylinder head with the aid of fastening screws. The fastening screws are usually guided through fastening eyes integrally molded on the cylinder head cover and are screwed to the cylinder head underneath in a loss-proof manner. For a tight seal, a gasket inserted into the supporting area between the cylinder head cover and the cylinder head is guided through the area of the fastening eyes on the cylinder head and is pressed in the fastening direction by the fastening screws. With this known approach, the tightness of the seal between the cylinder head cover and the cylinder head is ensured by pressing the gasket element in the direction of the fastening force created by the screws. The effective direction of the sealing force which is transmitted by the gasket element corresponds to the effective direction of the fastening force created by the fastening screws.

High restoring forces resulting from the pressure of the gasket element in the direction of the fastening force are transmitted from the compressed gasket element to the cylinder head cover and especially at higher temperatures may result in relaxation of the cylinder head cover, which is usually made of plastic. To prevent such relaxation, which can result in leakage, the contact pressure of the cylinder head cover against the cylinder head must be reduced, but this entails the risk that the seal tightness may be compromised.

This relaxation can be reduced by an increased number of fastening screws because this results in an approximately uniform surface pressure. Furthermore, an improved reinforcement of the cylinder head cover may also be achieved by additional ribs. However, both of these measures are associated with an increased weight of the cylinder head cover and additional manufacturing and/or assembly costs.

Furthermore, another factor to be taken into account is that the gasket is also subjected to sliding forces and shearing forces which cause additional stress on the gasket due to the different coefficients of longitudinal expansion of the plastic cylinder head cover and the cylinder head, which is usually made of aluminum.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide an improved cylinder head cover for a cylinder head of an internal combustion engine.

Another object of the invention is to provide a cylinder head cover which can be securely mounted on a cylinder head using simple measures.

A further object of the invention is to provide a cylinder head cover which ensures an adequate tight seal over a long service life.

These and other objects are achieved in accordance with the present invention by providing a cylinder head cover for a cylinder head of an internal combustion engine with a gasket element between the cylinder head cover and cylinder head, wherein the gasket element is associated with a sealing surface on the cylinder head or the cylinder head cover, and the gasket element comprises a vacuum chamber which is open on at least one side, the open side of the vacuum chamber facing the associated sealing surface on the cylinder head or cylinder head cover.

One advantage of the invention is that the gasket is constructed so that a vacuum supports the seal between the cylinder head and the cylinder head cover. Accordingly, a circumferential vacuum chamber is provided within the gasket element toward the side of the cylinder head or the cylinder head cover. As soon as a vacuum is applied, the gasket element is pulled against the respective component. This ensures a reliable seal. In an internal combustion engine, the vacuum may be generated by an external vacuum source. In automotive engineering, it is standard practice for a vacuum to be generated, provided and/or stored on the basis of the suction vacuum. This vacuum, which is available while the internal combustion engine is in operation, may be used for this sealing principle. If the internal combustion engine is not being operated and the vacuum declines, the vacuum in the vacuum chamber of the gasket element will also be reduced. In this case, however, contact between the cylinder head and cylinder head cover is still ensured, so this is not a disadvantage.

In accordance with to one embodiment, the gasket element comprises at least one lip-shaped profiled gasket for sealing the vacuum chamber. This sealing principle is extremely reliable and is also capable of compensating for minor unevenness.

In accordance with another embodiment of the invention, a fixation element is provided for securing the cylinder head cover on the cylinder head. If a vacuum is not available while the engine is shut down or is available only to a slight extent, the fixation element ensures reliable positioning of the cylinder head cover on the cylinder head. To accommodate the gasket element, a web is provided on the cylinder head or on the cylinder head cover, engaging at least partially in the vacuum chamber of the gasket element. By appropriately shaping the web and the vacuum chamber, it forms a loss-proof design, so the cylinder head cover can be assembled without any great complexity.

In accordance with yet another embodiment of the invention, the vacuum chamber is constructed so that the vacuum acts on both the cylinder head cover and the cylinder head. This eliminates a non-releasable fixation of the gasket element on one of the components. Fixation via the web described hereinafter, for example, is sufficient.

These and other features of preferred embodiments of the invention, in addition to being set forth in the claims, are also disclosed in the specification and/or the drawings, and the individual features each may be implemented in embodiments of the invention either alone or in the form of subcombinations of two or more features and can be applied to other fields of use and may constitute advantageous, separately protectable constructions for which protection is also claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in further detail hereinafter with reference to illustrative preferred embodiments shown in the accompanying drawing figures, in which:

FIG. 1 is a sectional diagram showing a sealing concept in accordance with the present invention;

FIG. 2 is a plan view of a cylinder head cover in accordance with the invention;

FIG. 3 is a detail view of a gasket element in an alternative variant of the present invention, and

FIG. 3 a is an enlarged diagram of detail X from FIG. 3.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The sealing concept according to FIG. 1 includes a cylinder head 10, which is designed to be essentially flat on its surface 11 facing upward. A cylinder head cover 12 lies on this surface indirectly. This cylinder head cover 12 serves to seal the valve drive and/or all the control elements arranged on the top side of the cylinder head. The cylinder head cover 12 is provided with a circumferential fastening edge 13 which also has a circumferential groove 14. A circumferential gasket element 15 is provided in this groove 14. The gasket element 15 has a web 15 a which extends into the groove 14 and it also has a circumferential vacuum chamber 16. This vacuum chamber is bounded by two sealing lips 17, 18 which also extend around the circumference and thus seal the chamber with respect to the surface 11 of the cylinder head 10. This gasket element 15 is adhesively bonded to the fastening edge 13 of the cylinder head cover 12, for example, and there is also the possibility or producing this gasket element by injection molding in a two-component injection molding process directly on the cylinder head cover with a thermoplastic elastomer, if the cylinder head cover 12 is made of a thermoplastic material. The vacuum chamber is connected to a vacuum source such as the intake manifold of an internal combustion engine. As soon as the vacuum is applied within the chamber, the cylinder head cover 12 is secured on the cylinder head 10. It is sufficient if the vacuum is in the range of 0.1 bar to 0.5 bar. A high fastening force is established for fastening the cylinder head cover because of the total effective area covered by the vacuum chamber.

FIG. 2 shows a cylinder head cover 12 in a view from above, namely from the side of the cylinder head. Like parts are identified by the same reference numerals. The gasket element 15, which is shown here as circumferential, sits in the corresponding groove 14 in the cylinder head cover 12. It is apparent that any gasket shapes can be designed with the gasket element. Since the vacuum acts uniformly along the entire gasket profile, there is no risk of bulging of the cylinder head cover due to variations in distribution of the contact pressure, which would result in leakage.

FIG. 3 is a sectional diagram of the cylinder head cover 12 illustrated in FIG. 2 with the gasket element 15. This gasket element can be seen again clearly in the enlarged detail X in FIG. 3 a. This is a vacuum seal with the vacuum chamber 20 which is open toward the cylinder head 10 through openings 21 arranged along the course of the gasket. The vacuum gasket here again has lips 25 facing the cylinder head. Furthermore, the vacuum chamber 20 is open at the top and forms a circumferential slot with the chamber into which a circumferential web 23 of the cylinder head cover 12 can be inserted. Passages 24 having a rectangular cross section are provided on the right side of the web 23. The gasket element 15 engages in the cylinder head cover 12 at these passages by means of a catch lug 26 integrally molded on the gasket element 15, so that the gasket element will be secured to the cover even when no vacuum is applied.

The foregoing description and examples have been set forth merely to illustrate the invention and are not intended to be limiting. Since modifications of the described embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed broadly to include all variations within the scope of the appended claims and equivalents thereof. 

1. A cylinder head cover for a cylinder head of an internal combustion engine with a gasket element between the cylinder head cover and cylinder head, wherein the gasket element is associated with a sealing surface on the cylinder head or the cylinder head cover, and the gasket element comprises a vacuum chamber which is open on at least one side, the open side of the vacuum chamber facing the associated sealing surface on the cylinder head or cylinder head cover.
 2. A cylinder head cover according to claim 1, wherein the gasket element comprises at least one lip-shaped profile gasket for sealing the vacuum chamber of the gasket element to the associated sealing surface.
 3. A cylinder head cover according to claim 1, wherein at least one fixation element is provided for fixing the cylinder head cover on the cylinder head.
 4. A cylinder head cover according to claim 1, wherein the gasket element is mounted on one of the cylinder head and cylinder head cover; the associated sealing surface is on the other of the cylinder head and cylinder head cover, and the vacuum chamber is in contact with said sealing surface.
 5. A cylinder head cover according to claim 1, wherein the cylinder head cover comprises a circumferential web which is received in a slot or groove in the gasket element.
 6. A cylinder head cover according to claim 5, wherein the vacuum chamber of the gasket element is open toward the web as well as toward the sealing surface on the cylinder head, and the circumferential web engages at least partially in the vacuum chamber. 